1. Field of the Invention
This invention relates to internal combustion piston engines of general application.
2. Description of the Prior Art
In most contemporary internal combustion piston engines, the balance of performance, efficiency, flexibility and longevity is less than optimum because of inherent limitations in their design.
In spark-ignition engines, this is due in large part to a fixed, lower than optimum compression ratio which is dictated by emissions considerations and the detonation pressure of the fuel. Engine torques are lower than optimum because of compromises in piston stroke. A long stroke is desirable because it generally yields a higher torque. However, the performance of long stroke engines is inhibited by the retarding effect on the pistons during their compression strokes. Relative short stroke spark-ignition engines are prevalent because a shorter stroke minimizes the retarding effect. However, short-stroke engines usually rely on a higher speed of operation in order to compensate for the lower torque. In turn, these high speed engines have a shorter life expectancy and suffer efficiency losses due to incomplete combustion and mechanical losses because of the need for large gear trains for speed reduction.
In compression-ignition engines a long stroke is more common, but the retarding effect is also a limiting factor. Hence, the maximum compression ratio is somewhat restricted by the retarding effect and the physical constraints of engine size. In addition, contemporary compression ignition engines, such as diesels, utilize high pressure fuel injectors to inject fuel into each cylinder at a precisely timed moment. These injection systems tend to be costly because they must be designed to operate reliably under high pressure conditions. The injectors often tend to foul with minute particles in the fuel and with carbon deposits due to incomplete combustion within the cylinders. Incomplete combustion is often due to changing load conditions which an engine having a fixed compression ratio cannot adapt to.
Several prior art attempts have been made to develop internal combustion engines of the spark-ignition type having compression ratios which may be varied according to the load conditions encountered. Some of these engines employ load response mechanisms which vary the position of an auxiliary piston (disposed in the same cylinder as the working piston) to vary the combustion volume and, hence, the compression ratio. In these engines, the auxiliary piston remains stationary during engine operation except when adjustment is made to change the compression ratio. However, because of their limited movement, these auxiliary pistons fail to receive adequate lubrication. It has also been proposed to employ two opposed working pistons to vary the combustion volume between the two pistons by changing the relative timing of the pistons. In these types of engines, all of the pistons are driven by means of crankshafts and connecting rods, the relative motions of the pistons being less than ideal for the attainment of optimum engine performance and efficiency. Furthermore, these solutions have not helped to solve the aforementioned problems inherent in prior art compression-ignition engines.